It's from a book called "Jelly Roll Quilts" by Pam and Nicky Lintott.
I used one jelly roll. First, sew 4 strips together to make strip sets. Then take two strip sets, place one on top of the other with right sides together matching seams, cut off the end selvedge, and cut those sets into 8 1/2" squares. Very carefully separate the squares, but keeping one set on top of the other, cut diagonally across each 8 1/2" square,to make triangles, always cutting in the same direction. You then sew the triangles into squares, and 4 of these squares make a block. It looks like the blocks are sewn on the diagonal, but they are not. Hope that makes sense.